The shorter of the two caps would be for "flat" (normal) response.
The 'presence peak' cap would give you more high-end. ( treble ) For example, when hiding the mic under a shirt, (which tends to muffle the sound) is the most common use.
The 'flat' response cap is 'recommended' for normal outside the shirt in plain sight mounting.
That said, I use the +4dB crisp response cap on my Countryman lavs 90% of the time. Hidden or not

The shorter of the two caps would be for "flat" (normal) response.
The 'presence peak' cap would give you more high-end. ( treble ) For example, when hiding the mic under a shirt, (which tends to muffle the sound) is the most common use.
The 'flat' response cap is 'recommended' for normal outside the shirt in plain sight mounting.
That said, I use the +4dB crisp response cap on my Countryman lavs 90% of the time. Hidden or not